The present invention relates to a machine for stamping, bending and/or mounting sheet metal parts, comprising a plurality of housing boxes which are vertically aligned and connected. Several housing boxes can be arranged in a row. Each housing box contains an upper housing part and optionally a lower housing part. The upper and lower housing parts are horizontally aligned and connected to each other in each housing box. Each housing part contains at least one carriage apparatus including a carriage guide, which engages a motor.
Moreover, the invention relates to a method for operating such a machine.
The present invention relates in general to an indexed advancing machining device in which a workpiece is subjected to stamping, bending, deepdrawing or other machining processes, wherein all machining processes are carried out by a cycled, indexed, stepwise advancement of the workpiece from one to the next processing step. The workpiece is thus subjected sequentially to a series of machining processes until the entire machining process is completed by the final process. The individual machining processes are carried out in a single system. Depending on the workpiece and the number of required process steps, a plurality of machines can be sequentially positioned in a modular arrangement according to EP 0 875 311. They are suitable especially for the mass production of sheet metal pieces because of their high production capacity, their short workpiece throughput times, and their high degree of automation.
EP-A 0 103 885 teaches a machine in which elongate upper and lower housing parts are connected to one another by spacing bodies at their ends to form a frame. At the front side and at the backside of each housing part, a number of carriage apparatus are fastened on which, in turn, corresponding tools are mounted for the workpiece to be produced, respectively. Worm gear shafts are provided in the housing parts and their end faces are flush with the housing parts. Several such housing frames can be connected to one another at their end faces wherein the connection of the drive shafts is realized by curved teeth couplings.
DE-A 195 35 949 teaches a machine in which housing parts extend between two vertical end beams, and the arrangement of several housing parts with their end face is not suggested.
EP-A 0 127 156 discloses a machine in which the housing comprises two horizontal supports and two vertical supports, wherein fixedly arranged torque output locations are provided in all four supports for coupling with a carriage apparatus.
DE-C 40 10 115 shows a machine for stamping, bending and mounting which, however, differs from the machine of the present invention in that the housing is used with closed front plates, wherein a central wheel is supported in the housing and a plurality of star-shape arranged carriage apparatuses are in driving engagement with the circumference of the wheel. Several such machine housings can be sequentially arranged in a modular fashion. The synchronization of the central wheels in all individual machine housings and, even more, of their starshape arranged and radially operating carriage apparatus is a problem because of the required angular gears and couplings.
The number of sequentially performed bending processes differs depending on the type of the product to be produced. Often, the bending device has a stamping device upstream; in some situations, however, the latter is not needed. The known machines are too large for simple bending parts because they are designed for eight or more carriage apparatuses or a multiple thereof. Even when all positions are not occupied by carriage apparatuses, angular gears that are not required, are running so that energy consumption and wear are unnecessarily high.
DE 195 36 036 teaches connecting individual machining units to a crankshaft drive so that the individual bending stamps can be activated or deactivated as selected. This is achieved by a piston cylinder arrangement which is moved by pressure medium actuation as a unit by the crankshaft so that the apparatus becomes active. By venting the cylinder, the apparatus is deactivated and the piston runs without load in the cylinder in a reciprocating fashion.
In EP 0 875 311 a system is described in which the stations are switched on and off as selected by engageable and disengageable bevel gears. These bevel gears are mounted on a spline shaft penetrating the machining units, wherein the energy and the movement of the individual machining units is delivered by a common drive motor to the individual machining units via the aforementioned shaft. The common drive shaft ensures that all machining units operate synchronously to one another and synchronously to the advancing cycle of the workpiece to be machined. If it is desired to produce a new workpiece on such a system of machining units, not only must the individual tools be exchanged and optionally individual stations be switched on or off, but also the respective tool stroke must be adjusted to the exchange of the eccentric apparatus. This requires an exchange of the eccentric discs which move the carriage apparatus. The eccentric discs also determine the carriage stroke because of their eccentricity. After the eccentric discs are exchanged, their angle adjustment must also be corrected so that the machining units move in a precisely timed manner with the advancement of the workpiece. Retooling times of four to six hours are required for such a tool exchange and adjustment of the machine to a workpiece that is to be newly produced. The cooperation of the workpiece advancement and the machining units must be precisely adjusted to each other with respect to timing and may not change even for working cycles of, for example, 500 strokes per minute. Due to the high cycle frequency for strokes of typically 40 to 50 mm, the machining units must not only receive considerable cutting forces but also considerable acceleration forces. Upon running in the machine, it is desirable that the stations can be operated individually, and a common reference position must be adjustable in a reproducible manner.
It is an object of the present invention to increase the productivity of a machine for stamping, bending, and/or mounting of sheet metal parts, and especially, to reduce the required retooling times for the adjustment of the eccentric discs.
A carriage apparatus is driven by a program-controlled synchronous motor. The movement cycle of the synchronous motor can be programmed. Instead of using an eccentric disc, the stroke can be adjusted easily by a program change. An exchange of eccentric discs is not required. Accordingly, the retooling time is advantageously reduced.
Because the controlling torque of the synchronous motor is exceeded due to high frequency and partially high shaping forces, it is advantageous for a gear, such as an eccentric disc, connecting rod, or elbow lever, to be positioned between the motor and carriage apparatus. High processing forces can be generated without the need for a large synchronous motor due to the corresponding gear reduction.
In connection with rotary gears such as eccentric discs, it is especially advantageous when the program-controlled synchronous motor is a rotation motor, preferably a torque motor, which is coupled to the carriage apparatus via the gear membrane. The stroke can be easily changed because the synchronous motor is operated only over a portion of its range. This means that the drive only employs a minimal angular range of the eccentric disc. This reduces the stroke. Accordingly, there is no need for a new eccentric disc. Neither an exchange of the eccentric disc is required during retooling nor the critical adjustment of the angular position for synchronization of the process steps. For both the running of the machine and the individual stations, respectively, the individual synchronous motor of the station can be controlled separately which facilitates control during retooling considerably. In this manner, individual stations can also be switched on or off as desired without having to mechanically intervene in the energy flow. This means that gear members such as movable clutches and angular gears are not needed.
In a further embodiment the motors of several sequentially arranged housing parts are exchangeable with one another. With such a standardized interface between the motors and the housing parts, the individual machine can be constructed very flexibly. Not only can individual stations be switched on and off electronically in a simple manner, but an excess number of motors can also be avoided, and they can be used in other machines or at other locations. The employed synchronous motors have an especially high output with a small volume when the motor is water-cooled. The resulting heat loss can thus be directly dissipated away from the machine. Problems with non-uniform heating of the machine are advantageously prevented. The machine maintains its precision even over extended production periods.
The individual housing parts can be sequentially arranged despite the water-cooled motors in a convenient, quick, and easy way when the housing parts have a cooling water inlet and cooling water return lines for the motors correlated therewith which are adjusted relative to one another in regard to their position. When connected sequentially, the individual housing parts form a common cooling water inlet and return line. These lines can be connected to one another, for example, by quick couplings.
In another embodiment the machine of the present invention comprises a memory-programmable control which comprises a current measuring device and an evaluation circuit which produces a signal as soon as set point limit values of a working cycle current are surpassed or no longer reached. As soon as a tool begins to turn dull, the required cutting and bending forces increase so that the current uptake of the motor also increases. Upon surpassing a predetermined limit value, the machine can thus be shut down and preventive servicing of the tool can be performed. Thus, the machine will not accidentally produce rejects. The same holds true when falling below a predetermined limit value, for example, due to tool breakage. When tool breakage occurs, the machine can also be shut down and a tool exchange can be carried out.
Also, the machine, upon surpassing or falling below the limit value, automatically will shut down. In this way, the machine will not accidentally produce rejects. As soon as tool breakage or tool wear occurs, which could lead to intolerable changes on the workpiece, the machine will automatically shut down.
The machine has a standardized and modular composition because the upper and the lower housing parts are components of a uniform narrow housing box whose front side has correlated therewith not more than one upper and one lower carriage apparatus. Such housing parts can be variably arranged in sequence and adjusted to the respective tool.
In certain situations it is advantageous where the torque motor has a continuous shaft which is provided with output hubs at both ends. For example, this allows symmetrical force introduction into a press by means of an elbow lever. Moreover, rear and front housing parts with their carriage apparatus can be driven by a common torque motor because the torque motor has two output shaft ends.
According to a further embodiment of the invention, the carriage apparatus is provided with eccentric discs which project past the narrow housing boxes such that between two neighboring housing boxes an optionally two-part spacer block is connected by screwing. This increases the spacing of the output shafts of neighboring housing boxes so that carriage strokes of 50 mm and more can be performed. Such simple intermediately positioned spacer blocks also allow a precise grid length and cutting length adjustment which may be required because of shaping of the workpieces during machining.
The machine according to a further embodiment has a front and rear housing box row wherein each front housing box is connected to a rear housing box at the top and bottom via a connecting plate and screws. As an alternative, connecting plates extending over the entire length of the housing box row can be provided. Both housing box rows have their own drive motors.
It is also advantageous to eliminate several drive motors for the individual carriage apparatus when a gear is connected between the motor and carriage apparatus and the gear is formed as a central wheel with pinions. The carriage apparatus is engaged with and driven by the gear wheel. A correspondingly stronger torque motor drives a larger central gear wheel. The pinions engage this central gear wheel and, in turn, drive the carriage apparatus whose axes are arranged radially to the axis of the central wheel. In this way, several carriage apparatuses can be driven simultaneously by a central wheel and the number of required individual drives is advantageously reduced.
The retooling time can be further reduced because the carriage apparatus is designed as a component group with the motor.
Moreover, it is an object of the invention to provide a method for operating the machine of the present invention while avoiding complicated exchange of eccentric discs.
The object in regard to the method is solved in that the rotation motor can be reversibly operated over only a selected angular range. Depending on the size of the angular range which is used, the stroke that is generated will change for the same eccentric disc. An exchange of the eccentric disc for the purpose of stroke change can therefore advantageously be eliminated.
The various features of novelty which characterize the invention are pointed out with particularity in the claims annexed to and forming a part of this disclosure. For a better understanding of the invention, its operating advantages and specific objects attained by its uses, reference is made to the accompanying drawings and descriptive matter in which a preferred embodiment of the invention is illustrated.